Twenty five patients, 14 males and 11 females with an average age of 75years with chronic Low Back Pain were tested before, during, and after 10minutes transcutaneous electrical nerve stimulation. It is important to consider the effect of TENS on the autonomic function because the pain pathway and the ANS pathway are somehow correlated to each other. There is still controversy among researchers who have reported the effect of TENS on autonomic function. So the purpose of this study is to measure the effect of TENS on the ANS and to see the relation of the pain control mechanism and the change in the ANS. The results were as follows : 1) Systolic blood pressure between before and during the experiment was apt to be a little increased, but statistically there was no significant change(P>.05). 2) Systolic blood pressure between during and after 10 minutes the experiment was apt to be a little decreased, but statistically there was no significant change(P>.05). 3) Systolic blood pressure between before and after 10 minutes experiment was apt to be a little decreased, but statistically there was no significant change(P>.05). 4) Diastolic blood pressure between before and during experiment was apt to be a little increased, but statistically there was no significant change(P>.05). 5) Diastolic blood pressure between during and after 10 minutes experiment was significantly decreased(P<.05). 6) Diastolic blood pressure between before and after 10 minutes the experiment was apt to be a little decreased, but statistically there was no significant change(P>.05). 7) Heart rate between before and during the experiment was apt to be a little decreased, but statistically there was no significant change(P>.05). 8) Heart rate between during and after 10 minutes the experiment was significantly decreased(P<.05). 9) Heart rate between before and after 10 minutes the experiment was significantly decreased(P<.05). 10) Skin temperature between before and during the experiment was significantly increased(P<.05). 11) Skin temperature between during and after 10 minutes the experiment was apt to be a little increased, but statistically there was no significant change(P>.05). 12) Skin temperature between before and after 10 minutes the experiment was significantly increased(P>.05). 13) Respiratory rate between before and during the experiment was apt to be a little increased, but statistically there was no significant change(Pgt;.05). 14) Respiratory rate between during and after 10 minutes the experiment was apt to be a little decreased, but statistically there was no significant change(Pgt;.05). 15) Respiratory rate between before and after 10 minutes the experiment was apt to be a little decreased, but statistically there was no significant change(P>.05).